Date: Wed, 29 Sep 2004 17:44:37 +0200
From: Andrea Arcangeli <andrea@novell.com>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Arjan van de Ven <arjanv@redhat.com>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Andrew Morton <akpm@osdl.org>
Subject: Re: heap-stack-gap for 2.6
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On Wed, Sep 29, 2004 at 03:24:46PM +0100, Alan Cox wrote:
> As the man page says
> 
> "Use of this option is discouraged."

and as a matter of fact the vast majority of mmaps executed by databases
with vlm are using MAP_FIXED ;)

I'm not saying databases themself are going to break with topdown, I'm just saying
there are applications out there making heavy use of MAP_FIXED, no
matter if the above manpage says it's discouraged. depending on
applications not to use it, isn't reliable and it's prone to break
randomly at runtime with topdown, this is my _only_ point, and it's a
tangible fact as far as I can tell (not a purerly theoretical issue like
the set_pte not being exceuted in asm).

If you want to make your kernel really safe, then disable MAP_FIXED and
return -EINVAL, then I agree it will be safe.
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